On building new greenhouses

The base frame:  2x8s.  The skinny bed is the path.

It’s going to take a couple of posts, but I wanted to show you the process of building a greenhouse (hoophouse, polytunnel, etc.) for my mom.  It’s a 10’x12′ complete kit from Growers’ Solution.  We’re doing two major beds in it with one long path down the middle (30″ wide x 12′ long).  This means the beds themselves are fairly deep at 3′-6″.  She understands that weeding will be, literally, a stretch, but she’s not concerned.  She’ll have 84 square feet of space under plastic to grow things, so, what’s a little stretching?

On the fated day, Easter,  that our daughter went into the hospital, I was playing Mother of the Year by actually building my own mother’s greenhouse’s base frame.  (I suppose that makes me Daughter of the Year.)  I used untreated 2×8 members:  short side (where the door is) are 10′ long, long sides and inner beds 12′.  They’re held together with galvanized lag screws with washers that are 3″ x 1/4″.  We assembled it on a flat surface (the driveway) then picked it up and moved it to where my mom wants it.  It wasn’t heavy; two people can lift it easily.

My mom and brother have removed all the grass in the beds.  As a precaution against all the moles tunneling in her sandy soil, they are going to bury some aluminum valley flashing (basically, thin metal) around the inside edges of the beds themselves so the little creatures cannot tunnel in.  It will go down about 6″ below the soil line.

Necessary tool:  hammer drill.  Self-tapping metal screws.  These are the tops of the hoops:  the ends fit into each other.  I put 4 screws in per connection.

Tonight after work I will hammer in the ground posts (galvanized steel tubes that are 2″ in diameter, 30″ long), level them, then put together then assemble the hoop frames.  I will likewise screw the hoops together on a level surface; it’s important to not have things too wonky.  These hoops will go into the ground posts and get screwed into them with metal-tapping galvanized screws.  This hoophouse is so small it only requires a center purlin; hopefully we’ll get that assembled and attached down the center too.

My brother hammers in the posts:  that’s a big bolt and washer they ship to hammer it in.  He’s using a 4 lb mallet.  Then we checked the level between the front and back with a line level.

I always fall down on the photo-taking.  Here we’ve erected the hoops and screwed them into the base poles.  We leveled the hoops by connecting the top purlin to the front and back hoops, made it level, fastened those hoops to their posts then leveled and connected the middle two.

And here’s a shot of how the base frame is connected and how the hoop is connected to the base poles.  I will connect the poles to the base by conduit (C-shaped) clamps.

And here’s the 1 1/2″ c-shaped conduit clamp:  never be afraid to pound something into the shape you need!  This is how I got it to fit in the corner.  I then tapped it back into the base pole.

Tomorrow morning I hope to erect the end walls. These are made of 2x4s; I intend to frame the door at one end and just a simple frame at the other.  (See the post below this one to see my own greenhouse’s end wall.)  The plastic will have to wait until another day!   Mom needs to get the topsoil/compost in place, and woodchips down the center aisle.  Then, it’s planting time.

Here’s another example of hammering something out to suit your needs.  This is a joist hanger/strap anchor.  I wrapped it up and over the top of this 2×4.  That’s the top of the greenhouse, top of the hoop you’re seeing.  I chamfered/birdmouthed the top of the 2×4 to accept the hoop.

And here’s something I didn’t have to monkey with:  it’s the top straps that hold the purlin (straight, horizontal pole) to the curved hoops.

And here’s our lovely ladder model showing the finished end walls.  All this work took only, what, 6 hours of my time!

13 responses to “On building new greenhouses

  1. Pictures, we need more pictures! Ha.

    Good point on the wide beds. I have 4 foot beds to maximize my space, and the ones on the edges of my (fenced) garden are a stretch. I have a handy 2 x 4 I lay across the bed so I can step in as-needed to reach a weed or harvest without compacting the soil. Not a bad solution.

    I thought we had invented this, but an acquaintance told me they used boards like that when working in tobacco fields growing up, who knew?

  2. You can be both mother and daughter of the year, and then your mom gets to be mother of the year because obviously she raised you right if you’re making her a hoophouse.

  3. This post is perfect timing, for me 🙂 I’ve been plotting and working hard in the back for months and I’m now finally getting the fenceline moved back to open up space for a greenhouse!! I’m so freakin excited!
    ….and I’m glad all turned out well for your girlie. Kids and the ER can be a nailbiting experience, usually more for the poor parents!

  4. I second the call for more photos when you get a chance.

  5. I have no construction skill whatsoever, but I still like seeing the process through your pictures… keep posting!

  6. I’m showing Ralph (the architect, originally from MI) your photos. He wants to know where did you get the hoops? I did one once with PVC pipes that i anchored in concrete blocks, but didn’t make it high enough, and never figured a good way to anchor the plastic covering… more pix, please, and xx oos to ‘the girl’

  7. “fall down on picture taking” – That’s called ‘being engaged in the project’ and is not a failure by any measure.

    Great info on the wood/metal interface, by the way – that’s the part I could never visualize.

  8. Thank you for the added pics! That looks entirely do-able and a simple, elegant design.

    – s

  9. What a nice project.
    What kind of wood are you using and how will you deal with rot/replacement?

  10. Sara, your use of the 2x indicates that good ideas just get around. Like bread, like pasta. I told my mom that’s the route she needs to go too and she was fine with that. I will do even more pics once I take on the chicken wire and plastic.

    Stefani, nah, I am just a hoophouse evangelist is all.

    Kathy, INDEED super exciting! You’ll love it. Like all new things there’s a learning curve but once you understand its quirks you too will be out stumping for these backyard bubbles of plastic. Just think of what you’ll save just in gas to get to the grocery store and back!

    Mme Slif, stay tuned. I am trying but sometimes I get caught up in the work 🙂

    MC, there’s not that much skill involved, believe me. The only tricky thing I have done is chop up the top of the end wall kind of funkily, otherwise if you can use a drill and a level then this too can be yours.

    Sharon, tell Ralph to stay tuned to next week’s installment which will be about plastic attachment. It’s not that difficult, really. I ordered some extra hardware to make the attachment more secure. And I updated this post to show where I got the greenhouse kit.

    Hi Jenn! Michigan misses you. And yeah, I am kind of all about getting things done when the task is at hand, so photos are low on the priority list. And really there’s no true instruction about how to attach the end walls or even the base to the poles, I just winged it with the experience I have and what’s available at the hardware store.

    Sara, it is simple, I give it that!

    Hi et! Well, knowing my mother she’ll either have moved to a new house or have reconfigured the greenhouse 3x before the wood will ever rot. I used untreated wood because there’s food grown in this greenhouse and so I didn’t want any leaching from the treated nasty stuff. Really, though, the hoophouse itself is self-supporting; the wood base is to hold the dirt in the beds and the end walls are a simple way to attach the door and the plastic. The benefit of the end wall is only slightly structural and that’s only for snow loads.

  11. Can we fly you in for a weekend and you can give us guidance? You make it seem so easy! : )

  12. Sure…it’s easy when you know what to do! And if you have the skills! And extra hands to help out! Still, it doesn’t look too terribly difficult…maybe some day when my life becomes stable once more…

    Happy hammering!

  13. Pingback: Reduce Greenhouse Shading « Gardora.net

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